Research map / Vision-language and multimodal / Cross-modal learning
MTSTRec: Multimodal Time-Aligned Shared Token Recommender
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Proposes MTSTRec, a transformer for multimodal sequential recommendation that fuses item ID, Gram-matrix style, LLM text, LLM-prompt text and price via one time-aligned shared token per item per layer.
Problem
Sequential recommendation in e-commerce often ignores temporal alignment across modalities (text, image, price, ID) in browsing sequences, and existing early/late fusion methods fail to capture cross-modal interactions per time step.
Approach
A transformer with separate per-modality encoders plus a time-aligned shared token per sequence position, averaged across modalities at each layer, so that each item's modality tokens exchange information at the same time step; style features come from VGG-19 Gram matrices and text/prompt features from Llama 3.1 embeddings.
Key results
- MTSTRec achieves NDCG@5 of 0.8800 on Food E-commerce vs 0.8512 for SASRec+ (best baseline).
- On House-Hold E-commerce MTSTRec reaches NDCG@5 0.8942, about 9.7% above SASRec+.
- On H&M (Trousers) MTSTRec reaches NDCG@5 0.2307, roughly 31.5%-43.7% above competing models.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use MTSTRec instead of the strongest baseline | Sequential recommendation · Food E-commerce | NDCG@5: 0.8512 -> 0.8800 | Helped |
| use MTSTRec instead of the strongest baseline | Sequential recommendation · House-Hold E-commerce | NDCG@5: 0.8401 -> 0.8942 | Helped |
| use MTSTRec instead of the strongest baseline | Sequential recommendation · H&M (Trousers) | NDCG@5: 0.1754 -> 0.2307 | Helped |
| add the item ID modality (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.7582(±0.0049) -> 0.8800(±0.0023); 0.7913(±0.0244) -> 0.8942(±0.0035) | Helped |
| add text and prompt-text modalities (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8574(±0.0013) -> 0.8800(±0.0023); 0.8191(±0.0047) -> 0.8942(±0.0035) | Helped |
| add the text modality (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8729(±0.0016) -> 0.8800(±0.0023); 0.8488(±0.0095) -> 0.8942(±0.0035) | Helped |
| add the prompt-text modality (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8749(±0.0046) -> 0.8800(±0.0023); 0.8770(±0.0035) -> 0.8942(±0.0035) | Mixed |
| add the style modality (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8784(±0.0020) -> 0.8800(±0.0023); 0.8932(±0.0093) -> 0.8942(±0.0035) | No clear effect |
| add the price modality (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8791(±0.0025) -> 0.8800(±0.0023); 0.8941(±0.0048) -> 0.8942(±0.0035) | No clear effect |
| use time-aligned TST instead of late fusion (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8211 -> 0.8800; 0.8773 -> 0.8942 | Helped |
| use time-aligned TST instead of early fusion (ablation) | MTSTRec · Food E-commerce and House-Hold E-commerce | NDCG@5: 0.8621 -> 0.8800; 0.8366 -> 0.8942 | Helped |
| use two shared tokens per time step instead of one (ablation) | MTSTRec · Food E-commerce | NDCG@5: 0.8800(±0.0023) -> 0.8795(±0.0022) | Hurt |
Surprising findings
- Removing item ID causes the largest drop (NDCG@5 0.8800 to 0.7582 on Food), while removing price barely changes results.
- Late fusion on Food drops NDCG@5 to 0.8211, lower than early fusion at 0.8621.
Limitations
- Evaluated only on three e-commerce datasets, two of which are proprietary.
- Gains over baselines are reported without variance across more datasets or external validation.
- Price contributes little to accuracy, so the price modality's value is unclear.
Experimental setup
Datasets: Food E-commerce (AviviD proprietary, released) House-Hold E-commerce (AviviD proprietary, released) H&M trousers purchases
Benchmarks: Food E-commerce House-Hold E-commerce H&M (Trousers)
Metrics: NDCG@5 NDCG@10 HR@5 HR@10 MRR@5 MRR@10
Baselines: SASRec BERT4Rec SASRec+ BERT4Rec+ MMMLP MMMLP+
Builds on: SASRec BERT4Rec attention bottleneck LLM-Rec Neural Style Transfer
Closest papers by meaning
- Harnessing Multimodal Large Language Models for Multimodal Sequential Recommendation (AAAI 2025 · similarity 0.87)
- MENTOR: Multi-level Self-supervised Learning for Multimodal Recommendation (AAAI 2025 · similarity 0.86)
- STAIR: Manipulating Collaborative and Multimodal Information for E-Commerce Recommendation (AAAI 2025 · similarity 0.86)
- Semantic Convergence: Harmonizing Recommender Systems via Two-Stage Alignment and Behavioral Semantic Tokenization (AAAI 2025 · similarity 0.86)
- LGMRec: Local and Global Graph Learning for Multimodal Recommendation (AAAI 2024 · similarity 0.86)
- Towards Unified Multi-Modal Personalization: Large Vision-Language Models for Generative Recommendation and Beyond (ICLR 2024 · similarity 0.86)
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